It's the same everywhere. If it's illegal to do crime and people go to jail why is there still crime.

Well at least for that corrupt politician, it seems like he'll have a hard time doing any future grifts

So don't bother holding them accountable at all? Why punish crime if it doesn't bring an end to crime?

Because they only punish them once they step out of their betters line. They sit on the evidence then use it once they can't get anything out of them anymore.